INVESTIGATION OF NITRIDE PHASES IN STAINLESS-STEELS BY NUCLEAR-REACTION ANALYSIS AND X-RAY-DIFFRACTION

Hard, wear-resistant TiN coatings on metals are mainly used when good coating adhesion to the substrate material can be obtained. However, i f the same treatment is carried out on different types of steel, marke d differences in coating adhesion are observed. Thus, to optimize the coating adhesion, it is necessary to know what phases and contaminatio n are present on the substrate prior the coating, and how these are af fected by the deposition process. Implantation of nitrogen at doses ra nging between 1 and 5 x 10(17) N+cm-2 is used to form the nitride in a ustenitic steels 304 and 310. Preliminary results are presented on the phases obtained with different plasma nitriding processes, measured u sing nuclear reaction analysis and X-ray diffraction techniques. No di fference is observed between the two types of steel, except when the s ubstrate is heated at 400-degrees-C after the implantation. At low dos es, only austenite, expanded austenite and gamma'-Fe4N are observed. W ith high doses, the diffraction patterns show the appearance of epsilo n-(Fe, Cr)2N1-x or Cr2N phases. Interdiffusion of nitrogen is demonstr ated when a Ti-TiN layer is deposited on an implanted sample.